Hello, I have some questions dealing with an interactive diagram. to access the diagram go here: http://www.colorado.edu/physics/phet/simulations/lens/lens.swf when you go there set the radius of curvature to 1.0 m, the refractive index to 1.6, and the diameter to 1.2 m Ok first question:1. Calculate the focal length of the lens. So I know I need to use the lens maker's equation. 1/f = (n-1) (1/R1 - 1/R2) Plugging in numbers is the answer: .83 cm? 2. Calculate the distance you need between the lens and the arrow so that its image is the same size as the object. What are your calculated values of p and q? What equation do I use to calculate this distance? Please help, muchas gracias.